StreamGetSzPtr
Using Stream::GetSzPtr to optimize the algorithm to count lines in Stream
StreamGetSzPtr.cpp
#include <Core/Core.h>
using namespace Upp;
int CountLines(Stream& s)
{
int n = 0;
int c;
while((c = s.Get()) >= 0)
n += c == '\n';
return n;
}
int CountLinesOptimized(Stream& s)
{
int n = 0;
for(;;) {
int sz;
const byte *p = s.GetSzPtr(sz);
if(sz) {
const byte *e = p + sz;
while(p < e)
n += *p++ == '\n';
}
else {
int c = s.Get();
if(c < 0)
return n;
n += c == '\n';
}
}
}
int CountLinesOptimizedSIMD(Stream& s)
{
int n = 0;
for(;;) {
int sz;
const byte* p = s.GetSzPtr(sz);
if(sz)
n += memcnt8(p, '\n', sz); // this is using SIMD..
else {
int c = s.Get();
if(c < 0)
return n;
n += (c == '\n');
}
}
}
CONSOLE_APP_MAIN
{
StdLogSetup(LOG_FILE|LOG_COUT);
const Vector<String>& arg = CommandLine();
if(arg.GetCount() == 0) {
RLOG("Please provide testing file path as argument, preferably >500MB");
return;
}
{
RTIMESTOP("Simple");
FileIn in(arg[0]);
RDUMP(CountLines(in));
}
{
RTIMESTOP("Optimized");
FileIn in(arg[0]);
RDUMP(CountLinesOptimized(in));
}
{
RTIMESTOP("Optimized SIMD (using memcnt8)");
FileIn in(arg[0]);
RDUMP(CountLinesOptimizedSIMD(in));
}
}
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